My 2000 TT couple recently starting blowing warm air. I consulted the Bentley manual which has a nice description of the system, but no real troubleshooting. Bentley does describe testing the high pressure switch connection by unplugging and jumping the plug side terminals. Jumping 1 and 2 should turn on the cooling fan, jumping 3 and 4 should engage the compressor clutch-- according to Bentley. When I jump 1 and 2 the fan does come on, but when I jump 3 and 4 I don't hear or feel the compressor clutch engaging. Any ideas what this means or what to pursue next? (Bentley is a very good manual-- but not for everything I guess).